Being in the glass business for 30 years I have come to know a thing or two about glass. It is a fascinating material. One term that I really like is safety glass. It doesn’t seem like those 2 words go together but they do. There are several types of safety glass or safer glass. Chicken wire or hammered wire glass, which you see used primarily in fire doors or exterior doors, has wire in the middle of it. this allows it break or crack but still keep its integrity.
In the automotive industry there are only 3 or 4 types of glass used on a car. Tempered, laminated, Plexiglas, and glass mirrors. 2 of them are safety type glass. I will break down what each is.
Tempered glass is used in vehicles as door, vent, sunroof and back glass. During the manufacturing process, tempered glass is heated to over 1,100 degrees. It’s then shot with cold air, which forces the glass to cool very rapidly. That process causes the outer surface to become much harder than the inner material. As a result, tempered glass shatters into tiny fragments with somewhat rounded edges when it’s broken. This was done so that large pieces of glass were not cutting people in car accidents. This was a great idea, but since the tempered glass completely falls out there is no further protection for objects coming from outside there care and it allows the occupants to be thrown out of the car, better wear those seat belts.
Laminated glass is used primarily for vehicle windshields. Two sheets of glass are bonded together by a plastic inner layer known as polyvinyl butyral. The inner layer softens the blow when anything hits the windshield. The inside rubber layer will prevent the glass from falling apart, and can stop many objects for penetrating the windshield itself. That, in turn, reduces the chances that you and your passengers will be seriously cut in the event of an accident or hit by a object thrown by a tire or falling off of another vehicle.
This is why they use laminate on the windshield and tempered glass everywhere else. The possibility of a flying object hitting your side windows or black glass and hurting is far less than the windshield. Mostly because you are traveling forward.
Think about this, on the original cars they used typical glass about 1/4 thick called plate glass, which had zero safety factors and was quite dangerous.
So now when you watch a Hollywood movie here a local Cincinnati or Dayton theather and you see someone punch a windshield and it breaks apart you will know it is just movie magic.